always try to bring fractions you need to compare to the same denominator (bottom number).
we have 9/10 of the pizza left.
then 4/5 if the pizza are eaten.
how to compare 9/10 with 4/5 ?
by bringing 4/5 also to a fraction of 10ths.
what do I need to multiply 5 with to get 10 ?
right, 2.
since we don't want to change the overall value of the original fraction, we need to multiply both levels (numerator and denominator) by that same factor :
4/5 × 2/2 = 8/10
aha !
that we can compare with 9/10.
so, when Lucas ate 4/5 (= 8/10) of the pizza, when there was originally 9/10 left, then we have 1/10 of the pizza left.
